Guardian Pipeline, L.L.C. operates as a gas transmission company. It operates a pipeline from Chicago Hub, Illinois and extends to Green Bay, Wisconsin. The company accesses North American supply basins, multiple upstream firm transportation providers, and multiple providers of storage and related services. The company was incorporated in 1999 and is based in Tulsa, Oklahoma. Guardian Pipeline, L.L.C. operates as a subsidiary of ONEOK Partners Intermediate Limited Partnership.